Method and apparatus for recovering and purifying refrigerant

Abstract

A method and apparatus for recovering and purifying refrigerant contained in a refrigeration system has a first mode of operation wherein refrigerant is withdrawn from the system being serviced, compressed, condensed and delivered in liquid form to a refrigerant storage means. The pressure ratio across the recovery compressor is monitored, and, when the pressure ratio exceeds a value above which the compressor may be adversely affected withdrawal of the refrigerant from the refrigeration system is terminated. The system is then operated in a closed, cooling mode wherein refrigerant recovered from the system and stored in the storage means is withdrawn therefrom by the compressor, compressed condensed, and expanded and returned to the storage means to thereby lower the temperature and pressure of the storage means and the refrigerant contained therein. Means for purifying the withdrawn refrigerant are located upstream from the compressor suction port so that refrigerant purification takes place during all modes of operation. When the temperature in the refrigerant storage cylinder falls to a predetermined level the system is returned to the recovery mode. During the second recovery cycle, because of the substantially lower temperature in the recovery system, the refrigerant storage cylinder effectively serves as a condenser.

What is claimed is: 
     
       1. Apparatus for recovering compressible refrigerant from a refrigeration system comprising; compressor means for compressing gaseous refrigerant delivered thereto, said compressor means having a suction port and a discharge port;   first conduit means for connecting the refrigeration system to said suction port of said compressor means;   condenser means for passing refrigerant therethrough, said condenser means having an inlet and an outlet;   second conduit means for connecting said discharge port of said compressor means with said inlet of said condenser means;   means for storing refrigerant;   third conduit means for connecting said outlet of said condenser means with said means for storing refrigerant;   fourth conduit means for connecting said means for storing refrigerant with said first conduit means;   first valve means operable between open and shut conditions and disposed in said first conduit means upstream from the connection of said fourth conduit means with said first conduit means;   second valve means operable between an open condition and an refrigerant expanding condition and disposed in said third conduit means;   third valve means operable between open and shut conditions and disposed in said fourth conduit means;   means for sensing a system control parameter related to protection of said compressor, and, for providing a signal having a value indicative of the sensed system control parameter; and   processor means for receiving said signal provided by said sensing means, and, for operating said first valve means to an open condition, said second valve means to an open condition, and, said third valve means to a closed condition in response to said signal having a value within a predetermined range at which said compressor is not adversely effected; and, for operating said first valve means to a shut condition, said second valve means to a refrigerant expanding condition, and, said third valve means to an open condition in response to said signal having a value within a predetermined range at which said compressor is adversely effected.   
     
     
       2. The apparatus of claim 1 wherein said means for sensing a system control parameter comprises; a first pressure transducer means for sensing the pressure of refrigerant entering said compressor and for providing a first pressure signal indicative of this pressure; and   a second pressure transducer means for sensing the pressure of refrigerant leaving said compressor and for providing a second pressure signal indicative of this pressure;   means for processing said first pressure signal and said second pressure signal to provide said signal having a value indicative of the sensed control parameter.   
     
     
       3. The apparatus of claim 2 wherein said means for processing said first pressure signal and said second pressure signal determines the pressure ratio across said compressor, said sensed system control parameter being compressor pressure ratio. 
     
     
       4. The apparatus of claim 2 wherein said means for processing said first pressure signal and said second pressure signal determines the pressure differential across said compressor, said sensed system control parameter being compressor pressure differential. 
     
     
       5. The apparatus of claim 1 further including means for purifying refrigerant, said means for purifying being disposed in said first conduit means. 
     
     
       6. The apparatus of claim 5 wherein said means for purifying refrigerant comprises; means for removing oil from refrigerant passing therethrough; and   means for removing acid, water and particulate contaminants from the refrigerant passing therethrough.   
     
     
       7. The apparatus of claim 5 further including liquid refrigerant accumulator means disposed in said conduit means. 
     
     
       8. The apparatus of claim 1 wherein said second valve means comprises; a flow control valve operable between open and shut condition; and   a refrigerant expansion means;   said flow control valve and said refrigerant expansion means being disposed in parallel fluid flow relationship in said third conduit.   
     
     
       9. The apparatus of claim 1 wherein said means for sensing comprises a temperature transducer positioned to measure the temperature of refrigerant being discharged from said compressor means whereby said system control parameter is the compressor discharge temperature. 
     
     
       10. The apparatus of claim 1 wherein said means for sensing comprises a pressure transducer positioned to measure the refrigerant pressure at said suction port of said compressor means, whereby said system control parameter is compressor suction pressure. 
     
     
       11. Apparatus for recovering compressible refrigerant from a refrigeration system comprising; compressor means for compressing gaseous refrigerant delivered thereto, said compressor means having a suction port and a discharge port;   first conduit means for connecting the refrigeration system to said suction port of said compressor means;   condenser means for withdrawing heat from and at least partially condensing refrigerant passing therethrough, said condenser means having an inlet and an outlet;   second conduit means for connecting said discharge port of said compressor means with said inlet of said condenser means;   means for storing refrigerant;   third conduit means for connecting said outlet of said condenser means with said means for storing refrigerant;   fourth conduit means for connecting said means for storing refrigerant with said first conduit means;   first valve means operable between open and shut conditions and disposed in said first conduit means upstream from the connection of said fourth conduit means with said first conduit means;   second valve means operable between an open condition and a refrigerant expanding condition and disposed in said third conduit means;   third valve means operable between open and shut conditions and disposed in said fourth conduit means;   first pressure transducer means for sensing the pressure of refrigerant prior to entering said compressor and for providing a first signal indicative of this sensed pressure;   second pressure transducer means for sensing the pressure of refrigerant leaving said compressor and for providing a second signal indicative of this sensed pressure;   processor means for receiving the first and second signals provided by said first and second sensor means, for processing the received signals to determine a pressure ratio across the compressor, and, for operating said first valve means to an open position, said second valve means to an open condition and said third valve means to a shut condition in response to said determined pressure ratio being lower than a predetermined value; and for operating said first valve means to a shut condition, said second valve means to a refrigerant expanding condition, and, said third valve means to an open condition in response to said determined pressure ratio exceeding a predetermined value.   
     
     
       12. A method for recovering compressible refrigerant from a refrigeration system, and, delivering the recovered refrigerant to a refrigeration storage means comprising sequentially the steps of; a. withdrawing refrigerant from a refrigeration system;   b. compressing the withdrawn refrigerant in a compressor to form a high pressure gaseous refrigerant;   c. condensing the high pressure gaseous refrigerant to form liquid refrigerant;   d. delivering the liquid refrigerant to the storage means;   e. determining the pressure ratio across the compressor;   f. monitoring the determined pressure ratio;   g. stopping the withdrawal of refrigerant from the refrigeration system when the monitored pressure ratio exceeds a predetermined value;   h. withdrawing refrigerant from the storage means;   i. compressing the refrigerant withdrawn from the storage means in the same compressor used to compress refrigerant withdrawn from the refrigeration system;   j. condensing the compressed refrigerant withdrawn from the storage means;   k. expanding the condensed refrigerant withdrawn from the storage means;   l. delivering the expanded refrigerant withdrawn from the storage means back to the storage means to thereby cool the storage means;   m. sequentially repeating steps h, i, j, k and 1;   n. while performing step m, monitoring the temperature of the storage means;   o. stopping the withdrawal of refrigerant from the storage means when the temperature of the storage means falls below a predetermined value;   p. resuming withdrawal of refrigerant from the refrigeration system when the temperature of the storage means falls below said predetermined value;   q. monitoring the suction pressure of the compressor; and   r. terminating the recovery operation when the suction pressure of the compressor falls below a predetermined value.   
     
     
       13. A method for recovering compressible refrigerant from a refrigeration system and delivering the recovered refrigerant to a refrigeration storage means comprising, sequentially, the steps of; a. withdrawing refrigerant from a refrigeration system;   b. compressing the withdrawn refrigerant in a compressor to form a high pressure gaseous refrigerant;   c. condensing the high pressure gaseous refrigerant to form liquid refrigerant;   d. delivering the liquid refrigerant to the storage means;   e. monitoring the temperature of the refrigerant being discharged from the compressor;   f. stopping the withdrawal of refrigerant from the refrigeration system when said monitored temperature exceeds a predetermined value;   g. withdrawing refrigerant from the storage means;   h. compressing the refrigerant withdrawn from the storage means in the same compressor used to compress refrigerant withdrawn from the refrigeration system;   i. condensing the compressed refrigerant withdrawn from the storage means;   j. expanding the condensed refrigerant withdrawn from the storage means;   k. delivering the expanded refrigerant withdrawn from the storage means back to the storage means to thereby cool the storage means;   l. repeating steps g,h,i,j and k;   m. while performing step 1, monitoring the temperature of the storage means;   n. stopping the withdrawal of refrigerant from the storage means when the temperature of said storage means falls below a predetermined value;   o. resuming withdrawal of refrigerant from the refrigeration system when the temperature of the storage means falls below said predetermined value;   p. monitoring the suction pressure of the compressor; and   q. terminating the recovery operation when the suction pressure of the compressor falls below a predetermined value.   
     
     
       14. A method for recovering compressible refrigerant from a refrigeration system and delivering the recovered refrigerant to a refrigeration storage means comprising, sequentially, the steps of; a. withdrawing refrigerant from a refrigeration system;   b. compressing the withdrawn refrigerant in a compressor to form a high pressure gaseous refrigerant;   c. condensing the high pressure gaseous refrigerant to form liquid refrigerant;   d. delivering the liquid refrigerant to the storage means;   e. monitoring the suction pressure of the refrigerant compressor;   f. stopping the withdrawal of refrigerant from the refrigeration system when said monitored suction pressure falls below a predetermined value;   g. withdrawing refrigerant from the storage means;   h. compressing the refrigerant withdrawn from the storage means in the same compressor used to compress refrigerant withdrawn from the refrigeration system;   i. condensing the compressed refrigerant withdrawn from the storage means;   j expanding the condensed refrigerant withdrawn from the storage means;   k. delivering the expanded refrigerant withdrawn from the storage means back to the storage means to thereby cool the storage means;   l. repeating steps g,h,i,j and k;   m. while performing step 1, monitoring the temperature of the storage means;   n. stopping the withdrawal of refrigerant from the storage means when the temperature of said storage means falls below a predetermined value;   o. resuming withdrawal of refrigerant from the refrigeration system when the temperature of the storage means falls below said predetermined value; and   p. terminating the recovery operation when the suction pressure of the compressor falls below a second predetermined minimum value.   
     
     
       15. The method of claims 12, 13, or 14, further including the step of purifying the withdrawn refrigerant, performed between steps a and b.